Cleanrooms are widely used for the manufacture, assembly and packaging of sensitive products and components where it is necessary for the various processes to be conducted in a controlled environment substantially free of particles and other potential contaminants. As such, cleanrooms are typically a confined environment in which humidity, temperature, and particulate matter are precisely controlled to protect the sensitive products and components from contamination by dirt, molds, viruses, noxious fumes and other potentially damaging particles.
Contamination control garments, such as disposable smocks, jumpsuits, gloves, shoe coverings, and hair coverings, are required apparel for the performance of many jobs. Some of the jobs requiring safety garments are performed in cleanroom environments, where the introduction of foreign matter must be minimized. For example, technicians in certain sensitive medical fields dealing with infectious matter, and working with ultrapure materials all wear contamination control garments in cleanroom environments. These garments perform the dual function of protecting the wearer from potentially hazardous materials and prevent unwanted matter from the wearer's person from contaminating the work product.
Disposable contamination control garments for use in clean room environments are typically made from nonwoven disposable materials, such as from sheets of spunbond/melt blown/spunbond (SMS) material and the like. Such sheets of material are cut into patterns and stitched together to form desired contamination control apparel.
Reusable contamination control garments are typically made from tightly woven continuous filament fibers. In some cases these wovens are calendered to improve the barrier properties. Continuous filament fibers are used as they tend to produce less particulates on washing.
Nonwoven fabric laminates are useful for a wide variety of applications. Particularly, nonwoven fabric laminates are useful for wipers, towels, industrial garments, medical garments, medical drapes, sterile wrap, and the like. Fabric laminates, such as spun SMS fabric laminates, made of isotactic polypropylene have achieved widespread use in operating rooms for drapes, gowns, towels, sterile wraps, foot covers, and the like. Such fabric laminates are well known as shown in U.S. Pat. No. 4,041,203 to Kimberly-Clark. Such SMS fabric laminates have outside spun-bonded layers which are durable and an internal melt-blown barrier layer which is porous yet which inhibits the penetration of fluids and bacteria through the composite fabric laminate. The layers are thermally bonded together by spot bonding in discrete areas of the fabric.
Broadly defined, particles may be any minute object in solid or liquid state with clearly defined boundaries, i.e., a clearly defined contour. Such particles may be dust, human skin or hair, or other debris. On a relative order of magnitude, a human will regularly shed 100,000 to 5000,000 particles of a size of 0.3 micrometer or larger, per minute. In some environments, such particles may be microorganisms or viable particles (i.e., single-cell organisms capable of multiplication, at an appropriate ambient temperature, in the presence of water and nutrients). These viable particles may include bacteria, moulds, yeasts and the like. Particles may come from the outside atmosphere, air conditioning systems, and liberation within the cleanroom by processes or by those who use the room. Every article and person that is brought into the cleanroom brings with it the potential of introducing such contaminants into the room.
The classification of cleanrooms by the ISO standards is based on the maximum number of particles of a certain size that can be present. For example, in microchip manufacturing, the cleanrooms are generally certified as ISO Class 3 environments. An ISO Class 3 environment may only have a maximum of 8 particles per cubic meter that are 1 micrometer or larger; 35 particles per cubic meter that are 0.5 micrometers or larger; 102 particles per cubic meter that are 0.3 micrometer or larger; 237 particles per cubic meter that are 0.2 micrometer or larger; and a maximum of 1000 particles per cubic meter that are 0.1 micrometer or larger. ISO Class 4 and 5 environments allow for an incremental increase in the particles present in the cleanroom which may be appropriate for less critical manufacturing environments than is necessary in ISO Class 3 environments.
Conventional SMS fabric laminates made of isotactic polypropylene have not achieved widespread use as garments and protective coverings in more demanding cleanrooms, particularly sterile cleanrooms, and in paint rooms because of the higher requirements for such uses and such SMS fabric laminates tend to emit particles after laundering, either particles from the fabric itself or by passage of particles from the wearer to the atmosphere. The present invention describes a fabric that overcomes the shortcomings of conventional laminates in this regard.